This invention relates to an intake device for an outboard engine and more particularly to an improved induction system for a two-cycle crankcase compression engine having vertically disposed crankcase chambers.
Many multiple cylinder, two-cycle, crankcase compression, internal combustion engines operate with their cylinders and crankcase chambers vertically disposed relative to each other. This orientation is typical, for example, in an outboard motor wherein the engine has its crankshaft rotatable about a vertically extending axis. As a result, if multiple cylinders are employed normally one cylinder is spaced vertically above the other and the same is true with respect to the sealed crankcase chambers of the engine. This may be the case with either in line engines or the type of engines wherein the cylinder banks are staggered relative to each other so that the pistons and, accordingly, the crankcase chambers are vertically disposed one relative to the other.
There are advantages to providing a separate charge forming device for each crankcase chamber or, alternatively, an individual barrel of a multiple barrel carburetor serves each crankcase chamber. For example, a two barrel carburetor is employed to serve two vertically spaced crankcase chambers of an engine and the carburetor is disposed in a normal orientation so the carburetor barrels are disposed on the same horizontal plane. If the carburetor barrels are aligned with the center of the intake passage for the crankcase chambers, the manifold will have a passage that extends from one carburetor barrel upwardly to one crankcase chamber and a passage that extends from the other carburetor barrel downwardly to the other crankcase chamber.
In connection with a manifolding arrangement of the type described in the preceding paragraph, there can be difficulties in insuring good engine running due to the fact that the intake manifold passages slope in opposite directions to each other. A reason for this is that the fuel has a tendency to condense and there will be different amounts of back flow of the fuel depending upon the direction of inclination of the intake passages. As a result, previously proposed induction systems of this type have resulted in engines which run poorly under certain running conditions.
It is, therefore, a principal object of this invention to provide an improved induction system for a multiple chamber internal combustion engine of the two cycle crankcase compression type.
It is a further object of this invention to provide an induction system for a multiple chamber two-cycle crankcase compression internal combustion engine that permits the use of a two barrel carburetor and still achieves even running.
It is a further object of this invention to provide a system for insuring equal mixture strength to two adjacent cylinders of an engine having its output shaft rotating about a vertically extending axis.